MRI machines are used to detect signs of a wide variety of diseases, including cancerous tumors, Parkinson's, Alzheimer's, Huntington's disease, and multiple sclerosis. MRI was originally called “Nuclear Magnetic Resonance Imaging” because the way that an MRI machine works is that the magnet inside the machine causes the body's water molecules to align themselves with the magnetic field. The “Nuclear” in the name refers to the atomic nuclei, not to nuclear radiation. Unlike a CAT scan, an MRI does not produce radiation.

This enables the MRIs computer to produce detailed images of any section of the body, and technicians can recognize problematic patterns in the brain or elsewhere in the body. With a traditional MRI machine, a patient must lie in a narrow tube, which can cause problems for people who have claustrophobia, since an MRI scan can take up to an hour. It is also not always practical for those who are obese.

An open MRI machine is much less claustrophobic. There are a few different types of open MRI machines. Some open MRIs are formed more like rings than tunnels, so that only one part of your body is in the MRI at once. Others can even examine a patient in an upright position.

One criticism of some open MRI machines has been that the resolution is not always as good as it is with the traditional tunnel-shaped MRI machine; however, technological improvements have increased image quality greatly in some open MRI machines. Your doctor should be able to tell you which kind of machine is best for you.

Note that anyone with a pacemaker or other metal in the body will not be able to use an MRI machine. However, a CAT scan is also effective at detecting potential problems, and in some cases, depending on the possible problem, better. Your doctor may order either a CAT scan, a traditional MRI, or an open MRI, depending on your individual circumstances.